1. Field of the Invention
An aspect of the invention relates generally to a sanitary washing apparatus, specifically relates to a sanitary washing apparatus for washing such as a “bottom” of a user seated on a sit-down toilet stool with water.
2. Background Art
When a washing nozzle for washing the body, such as the “bottom”, of a user seated on a toilet seat squirts wash water at the body, at least part of the washing nozzle is exposed (advanced) outside from the casing installed with prescribed functional components including the washing nozzle and a hot water tank. Hence, dirt and dirty water may be attached to the washing nozzle. In this context, there is a sanitary washing apparatus which cleans away dirt and dirty water attached to the washing nozzle before and/or after body washing. This keeps the washing nozzle clean.
However, in a humid environment such as a toilet room, even after dirt and dirty water attached to the washing nozzle are cleaned away, bacteria may grow on the washing nozzle over time. More specifically, bacteria such as methylobacteria, called pink slime, and black mold grow on the bowl surface of the toilet stool. Such bacteria may be attached to the washing nozzle and multiplied thereon. Multiplication of bacteria results in an aggregation of bacteria and their secretion (slime, black stain), called biofilm, for instance. The biofilm is difficult to remove by the normal nozzle cleaning as mentioned above.
In this context, Japanese Patent No. 3487447 discloses a private part washing apparatus in which an electrolytic cell is incorporated as a nozzle cleaning water producing part. In the private part washing apparatus described in Japanese Patent No. 3487447, when tap water is used as cleaning water, chlorine contained therein is electrolyzed and chemically changed to hypochlorous acid. This can serve as an acidic chemical for cleaning. Hence, effective cleaning can be performed on dirt such as resulting from ammonia in particular.
Here, to efficiently use the cleaning water produced in the electrolytic cell, it is more preferable that the electrolytic cell be provided closer to the nozzle. Thus, JP-A-2005-155098 discloses a private part washing apparatus in which an electrolytic cell is provided on the flow channel on the downstream side of the hot water tank. In the private part washing apparatus described in JP-A-2005-155098, hot water in the electrolytic cell is electrolyzed into electrolytic water. The nozzle cleaning means squirts the hot water as cleaning water at the bottom washing nozzle and the bidet washing nozzle.
However, electrolysis of hot water into electrolytic water is likely to result in producing e.g. calcium carbonate, known as “scale”. Scale attached to the electrode of the electrolytic cell causes the problem of decreased production capacity of electrolytic water.
In this context, in order to remove scale, the private part washing apparatus described in JP-A-2005-155098 inverts the polarity of voltage applied to the electrode. Likewise, JP-A-10-034156 discloses an electrolytic cell control apparatus including a polarity switching means for switching the polarity of the anode side and the cathode side of the electrodes of the electrolytic cell. In the private part washing apparatus and the electrolytic cell control apparatus described in JP-A-2005-155098 and JP-A-10-034156, respectively, the produced scale is detached from the surface of the electrode by polarity inversion.
However, if a large amount of scale is produced before performing polarity inversion, in a sanitary washing apparatus with a relatively narrow flow channel, the flow channel may be clogged with scale detached from the electrode. Furthermore, after private part washing, even if heating means such as a hot water tank is not in operation, the flow channel and the electrolytic cell are filled with hot water for the private part washing. Thus, scale is produced even after private part washing, and the amount of the scale may become larger. On the other hand, if polarity inversion is performed frequently, the problem is that the electrode of the electrolytic cell is degraded earlier, and the lifetime of the electrode becomes shorter.